Computer terminals and peripherals have become dramatically smaller and more portable. Personal computers and peripherals are small enough to sit on the desk at work. Smaller still are lap top computers and notebook computers. There are computer terminals which are small enough to be mounted in a vehicle such as a delivery truck. Still smaller are the hand held terminals typically used for their portability features where the user can carry the terminal in one hand and operate it with the other. A physical connection of the above devices by means of cables or fibers might have drawbacks, such as configuration constraints because of the limited length of the cable, limited number of ports on the computer thus limiting the number of peripherals that can be attached, cumbersome reconfiguration of hardwired devices, etc. Note that there are some cable or fiber based communication systems where the limited number of ports on the computer does not really limit the number of peripherals Ethernet is one example of a communication system where the cable is used as a shared medium (other examples are token ring, FDDI (Fiber Distributed Data Interface), and DQDB (Distributed Queue Dual Bus)).
The smaller the devices get, the more important it becomes to replace fixed physical connections by wireless ad-hoc connections (e.g. body networks, radio frequency connections, or infrared connections), since physically connecting the computer terminals, peripherals, and other devices by means of cables or fibers severely reduces the efficiency gained by making the units smaller. Ad-hoc connections are required where devices move around, enter an area and exit the area. The term ad-hoc refers to the need for frequent network reorganization.
Local area communications are rapidly evolving into what can be called personal local area networks, which are networks for communication between local peers or subsystems. These kind of networks will herein be referred to as local networks. Wireless communication is of particular importance in such local networks. There are different wireless communications approaches known that have been developed and designed with an eye on the communication between peers or subsystems of such local networks.
EP 1 022 876 A1 discloses an apparatus for exchanging service information with other devices. The presented apparatus comprises a transceiver, a processing unit, a memory for storing information about its local services and/or services provided by other devices, and a protocol resource manager. In an initial step the protocol resource manager triggers the transceiver to send service information, comprising information about itself and/or other known devices to other devices. Then it chooses a time-out value TA and ensures that the apparatus listens for up to a maximum time TA for service information received by said transceiver. If TA timed out without having received such service information by said transceiver, the resource manager triggers said transceiver to start with the initial step. If such service information was received by said transceiver prior to TA timing out, the resource manager checks whether said service information received comprises current and accurate information about itself. If yes, it chooses another time-out value TA and continues with the step of ensuring that the apparatus listens for up to a maximum time TA. If no, then the same behavior is observed, excepting that TA is chosen from an earlier time range than normal.
Furthermore, a scheme for advertising service offerings in a communications system is presented. The scheme comprising two devices, wherein a first of said two devices in an initial step sends service information, comprising current and accurate information about itself and/or other known devices. In a next step it chooses a time-out value TA. Then it listens for up to maximum time TA for service information sent by another device. Subsequently, if TA has timed out it continues with the initial step, otherwise it checks whether or not service information sent by another device comprises information about itself (local services). If yes, then it continues with the step of choosing a time-out value. If no, then the same behavior is observed, excepting that TA is chosen from an earlier time range than normal.